That's summer camp as presided over by Hamas and Islamic Jihad. The kids play in the waves, play football and other, er, games. And they learn things as well:
Zidan Obied, who is running this camp, explains the programme and philosophy. "We are expressing our principles as Islamic Jihad. We believe in the right of resistance and we are against peace negotiations."
He runs through some of the daily activities: sessions on the history and geography of Palestine; readings from the Qur'an; arts and literature; drawing – "we teach them to draw maps of Palestine from the river to the sea"; lessons on the significance of Jerusalem and the al-Aqsa mosque; sports; volunteering activities such as tree-planting and clearing cemeteries; military-style marching and exercises.
This, of course, is for the boys. There are separate camps for girls, with "very limited" sporting activities. Instead they are taught crafts, such as embroidery.
Along the beach, so to say, the boys' activities include playing 'sniper's corner' and the girls are 'studying the Qur'an for five hours a day':
"Of course we have a political agenda," says Ahmed Nabil, a Hamas official helping to run the camp. "We believe the older generation has a duty to tell the younger generation about these issues. We are letting them play but also giving them a message. We must not let them forget that we are an occupied people."
It's all there: 'from the river to the sea' means one day no more Israel; 'under occupation' merely neglects the detail that Gaza's disoccupation was used as an opportunity to start tossing missiles at Israeli population centres; and those girls are doing embroidery in a much more limited range of activities than is laid on for the boys.
This is for the children, those carrying the hopes and dreams of Palestine's future. And still there are Western liberals and leftists - or so they would describe themselves - happy to agree that this is a kind of politics one can support; happy to agree that the problem of Israel-Palestine is exclusively due to Israel.
Even on a Friday afternoon, with the weekend coming into view, it's kind of mystifying.